The overall goals of this program remain directed towards a better understanding of cellular regulation. The individual components of the program are: 1. Bone marrow transplantation of HLA-matched and haploidentical patients. Specifically, bone marrows will be depleted of mature T cells by the use of anti-Leu 1 antibody plus complement. The engraftment, graft versus host disease and immune reconstitution of these patients will be evaluated. Animal models will be employed to study engraftment and graft vs. host disease. 2. The cell-cell interactions which regulate erythropoiesis and in particular hematopoiesis in human and murine systems will be studied. We have partially purified progenitor cells and we are currently studying the effect of cloned CSF-GM on their differentiation. Also the effects on hematopoiesis of stromal cell CSF is being investigated.